The invention relates to apparatus for the cold drying of gas, in particular of compressed air, including a heat exchange means and a drying means in an integral unit, through which a cold-carrying medium flows to cool the gas to such a temperature that the moisture present in the gas is precipitated as a condensate.
Generally speaking moisture, as a rule water vapour, is contained in gases under atmospheric conditions, but there may also be quantities of other substances which are volatile at elevated temperatures. This applies in particular to gases which are under pressure.
For drying gases, in particular compressed air, above 0.degree. C. cold dryers are employed and below a temperature of 0.degree. C. and below the pressure dew point adsorption or absorption dryers are employed.
In the cooling or cold condensing of gases such as air this takes place--in so far as drying is necessary--in a separate step, after which it is then cooled down to the desired value. Accordingly two independent and separate units are required.
Accordingly, the cold drying of gases results in problems both from the energy point of view as well as from the structural aspect.
Apparatus having favourable energy consumption for the cold drying of gases is known from DE-A-39 41 713. This employs two heat exchangers, the main heat exchanger employed for the cooling having a pre-heat exchanger connected ahead of it, in which the incoming gas is cooled by the already dried emerging gas. In order to prevent icing-up, which can lead to failure of the equipment, heat transfer is restricted so that undisturbed operation is achieved. This requires special measures to be taken in construction, and a substantial outlay in control equipment.
It is the aim of the invention to provide apparatus of simple construction and effective operation for the cold drying of gases, in which the danger of icing-up is eliminated.